ES2402783T3 - Variable priority of network connections for priority projection - Google Patents

Abstract

A method for operating a network of a procedure for operating a communications network that has a plurality of links or communications that has a plurality of links and that carries a plurality of network connections that carries a plurality of network connections comprising: determining one priority of each d comprises: determining a priority of each of a plurality of network connections provided for a plurality of network connections intended to communicate by a communication link based on communicating by a communication link based on a corresponding predetermined stop time at a corresponding predetermined stop time; detect (30) a failure in the client link; detect (30) a failure in the communications link at a point at time T; calculate unifications at one point at time T; calculate a real stop time for each of the plura a real stop time for each of the plurality of network connections of an amount of network connection interim of a quantity of interruption that has occurred during a time period that has occurred during a predetermined period of time up to time T; calculate a predetermined type up to time T; calculate an allowed stop time for each of the allowed multi-stop times for each of the plurality of network connections from a quantity of network connections from a quantity of interruption allowed over the period of tid of interruption allowed on the predetermined period of time; calculate a predetermined stop time; calculate an expected stop time for each of the plurality of connection expected for each of the plurality of network connections of an expected amount of network interruption of an expected amount of interruption from time T to an end of the period from time T until the end of the predetermined period of time; protect the plurality of predetermined time; protect the plurality of network connections from failure in the common link network connections from the failure in the communications link according to the determined priority of each unit according to the determined priority of each of the plurality of network connections, in which one of the plurality network connections, in which a network connection with a higher priority is a network connection with a higher priority supplants a connection with a lower priority; and establishes a connection with a lower priority; and updating (34) the priority of each of the pluralize (34) the priority of each of the plurality of network connections from a time to network connections from a time from the calculation of the time of actual stop and the calculation of the real stop time calculation and the allowed stop time to increase the priority stop time allowed to increase the priority for each of the ad connections plurality for each of the network connections plurality as the Actual stop time is approached as the actual stop time approaches the allowed stop time for each one of the allowed stop time for each of the plurality of network connections. plurality of network connections.

Description

Variable priority of network connections for priority projection

Background of the invention

[0001] The present invention relates to traffic protection techniques in optical and electronic networks.

[0002] When a link in an electrical or optical network is broken, the traffic capacity between the two nodes of the broken link is necessarily reduced until the link is restored. Several protection techniques are used to ensure that nevertheless the network connections that use the link are maintained. This is done by changing the route of the signals around the broken network link, which can be done using different protection techniques. Protection techniques classify network connections using the link by priority.

[0003] For the user of a network connection, the protection level of a network connection is typically defined by a Service Level Agreement (SLA) with a network service provider (SP), essentially the administrator of the network net. The SLA guarantees that a network connection will not have more than a certain amount of downtime, during which time the network connection is lost. The SP uses the protection priority to ensure the desired level of protection for the user of a connection. However, the resulting protection service techniques only support one type of guaranteed level of protection: total protection, almost no downtime (availability called 99.999%). This is true for connection-oriented technologies, such as SONET / SDH (synchronous optical network / synchronous digital hierarchy), as well as packet flow technologies, such as MPLS (Multiprotocol Label Switching), RPR (Resilient Packet Ring ), etc. Therefore, it should be understood that network connections as understood herein include not only circuit connections, but also packet flows.

[0004] The different protection techniques theoretically allow different levels of priority, so that users of the network with higher priority are ahead of users with lower priority to ensure that their network connections are maintained. However, the priority levels are fixed and the highest priority network connections simply maintain their preferential right to purchase network connections with a lower priority to ensure a "hierarchy" of connectivity. These techniques do not necessarily guarantee that the downtime of the connection does not exceed its allowed downtime if the priority of the connection is not at the highest level. US 2005/160171 describes the traffic engineering and bandwidth management of packaged links that may require the selection of one of a plurality of component links in a link package for use in the admission of a connection that requires admission . While making the selection, it can be determined that more than one of the component links has the necessary resources to support the connection. An admission policy can then be selected from a plurality of admission policies. On the basis of the selected admission policy, a particular component link can then be selected.

[0005] Therefore, current protection techniques do not guarantee a protection level below a complete protection to a network connection. There is no way to reduce the amount of protection bandwidth and at the same time provide a significant protection guarantee for all connections affected by a network failure based on each SLA connection.

Summary of the Invention

[0006] The present invention is defined in the appended claims.

Brief description of the drawings

[0007] Figure 1A illustrates a simplified communications network with only two nodes;

Figure 1B is a table of connections of the network of Figure 1A with SLA requirements.

[0008] Figure 2 is a flow chart of network mesh operations according to an embodiment of the present invention.

[0009] Figure 3 is a flow chart of ring network operations according to another embodiment of the present invention;

[0010] Figure 4 illustrates a communications network with a network management station and a network billing system, and

[0011] Figure 5 depicts an organization of a network node, a network management station or a network billing system, in accordance with an embodiment of the present invention.

Detailed description of the invention

[0012] An example illustrates the problem of the current use of priority in the restoration of network connections in communications networks. In a simplified example of a two-node network 10 shown in Figure 1A, there are two links 11 and 12 between nodes 13 and 14. The network has network connections with traffic classes A, B, C and D that define the allowed idle time, the allowed amount of cut, which is set in the network connection SLA. The downtime of each class is shown in the table in Figure 1 B.

[0013] If it is assumed that the actual downtime of faults on both links 12 and 13 amounts to 3 hours per year and that there is no protection bandwidth in network 10, traffic protection for network connections of one class should be prioritized against the traffic of network connections of other classes. In existing preferred subscription designs, the traffic of connection classes A and B has a higher priority than that of the connection of classes C and D, and that traffic is anticipated. As a result, class A and B connections have zero downtime, while class C and D connections disconnect for 3 hours. This is true regardless of how traffic is routed. As a result, the SLA is violated for class C connections.

[0014] Instead of being fixed, the priorities of the different network connections are determined in response to link failures and dead times resulting from the network connections in accordance with the present invention. Variable priorities can ensure that the SLA of each connection is not violated or at least minimally violated. With respect to the example network 10 of Figures 1A and 1B, an embodiment of the present invention gives priority to the traffic of class C connections for 2 hours. Once the idle time approaches the allowed idle time (defined by the SLA of each connection), the priority of class C connections rises above that of class B connections. Therefore , class B traffic is preceded during the remaining hour, and the SLAs of all connections are satisfied.

[0015] It should be noted that the present invention is independent of the protection protocols used in different communication networks. Thus, the present invention is not particularly interested in the way in which a particular network puts circuit connections or packet streams, such as RSVP (Resource Reservation Protocol) or SONET APS (automatic protection switching), or packet preference requests IP. Rather, the present invention relates to how priorities for circuit or packet priorities are determined.

[0016] The present invention determines the priority of a network connection so that the priority can be sensitive to the idle time of the actual connection, the allowed idle time, and even its expected idle time. Actual idle time is the actual amount of break that occurred during the predetermined period of time up to a time T. The allowed idle time is the allowed amount of connection interruption for a predetermined period of time, typically one year . This is stated in the SLA (Service Level Agreement) between the user connection and the SP (Service Provider) of the connection. The expected stop time is the expected amount of interruption from time T until the end of the predetermined period of time. Priority can be determined in many ways and the following descriptions of examples illustrate how priority can be varied. The variable priorities of the connections are then used to re-establish the connections after a network failure.

[0017] Mesh network operation

[0018] According to an embodiment of the present invention, a method of operating the network is illustrated by the flow chart of Figure 2. During the operation of the network, as indicated by the dotted arrow of the top of the drawing, step 30 detects the failure of a link in the network. This detection depends on the particular network communications protocol, and is well established for and known by network designers. For example, the already long established SONET / SDH protocol provides a link failure detection in several optical networks.

[0019] Given the failure event, step 31 determines the set of network connections F that are directly affected by the failure at time T. The time T is defined from the beginning of the SLA period, say, for example, at the beginning of each calendar year, for connections. For each connection f of the set F, in step 32 several alternate routes not affected by the failure to recover that connection are considered. At time T these alternative routes usually carry other network connections and could have available or free bandwidth, that is, unused capacity, to carry more connections. To recover or protect the network connection f, by using an alternative route, the available bandwidth can be used, or other connections can be substituted or "pushed" out to the alternative routes.

[0020] According to an embodiment of the present invention, step 34 calculates the priorities of network connections i at time T. The priority can be defined in many different ways and the following is a simple example:

Priority (i, T) = 1 if Actual Disconnection (i, T)> SLA (i), OR

otherwise Priority (i, T) = 0;

where SLA (i) is the interruption of the maximum allowed, or the idle time, according to the SLA, and Actual Disconnection (i, T) is the actual amount of idle time that the connection i has experienced since the beginning of the period of SLA. Connections i in set 1 include not only connections that have failed from set F, but also connections that already occupy alternative routes. This prioritization gives priority to users who have not yet exhausted their allowable interruption time, SLA (i), regardless of how close / far they are from violating their SLA. This priority determination is very simple, but it is still much better than the current situation of fixed priorities.

[0021] Of course, other variable prioritizations are possible. For example, you can define a Slack (i, T) function that measures the amount of tolerance a connection i has for an interruption in time T under the network connection SLA. The Slack function is used to determine the priority based on the allowed idle time, the actual idle time and even the expected idle time of the connection. For example:

Slack (i, T) = SLA (i) - ActualDown (i, T) - (LT> ExpectedDown (i)

where ExpectedDown (i) is the expected downtime for the entire SLA period for connection I and the probable downtime during the rest of the year is (lT) "ExpectedDown (i, T). In this example, the priority also it is a function of the idle time, in addition to the allowed idle time and the actual idle time, therefore, the priority can be set as:

Priority (i, T) = MaxPriority - Slack (i, T) where MaxPriority is the highest priority a connection can receive.

[0022] Returning to the flowchart of Figure 2, step 34 therefore determines the priorities of all

connections F. The prioritized network connections and the set of victims V, the set of non-prioritized network connections, are selected in step 38. First, the priority is used for network connections f to first consume the Available free bandwidth and then prioritize previously occupied alternative routes. The non-prioritized network connections are in set V. Then the process flow waits for the next link failure. Even if the network decides to appropriate a connection and the downtime is long enough to risk an SLA violation of the connection, the prioritized connection can be reconsidered in the next failure event based on its new highest priority and A different connection may cease to be prioritized.

[0023] Ring network operation

[0024] The present invention is adaptable to ring networks. In a ring network the operation according to the present invention is simpler since alternative routing is trivial compared to a mesh network. However, determining an optimal V, the set of connections that should not be prioritized, is still difficult. The example flow chart of Figure 3 shows the operations according to an embodiment of the present invention.

[0025] Step 40 detects the failure of a link in the ring network during normal network operation as indicated by the dotted arrow at the top of the drawing. As stated earlier, fault detection is dependent on the protocol of the particular communications network, and is well established for and known by network designers. In step 41 the slack (i, T) defined above is calculated for all connections, including failed network connections and alternative route connections, typically network connections in the opposite direction around the network in ring from the connections that have failed. In step 42, a network connection that has failed f with the smallest slack (f, T) is selected, and by step 44 the connection f is alternately routed around the other side of the ring network. Any network connection c with the highest slack (c, T) is selected for prioritization.

[0026] In decision stage 46 it is verified whether slack (f, T)> slack (c, T). If the statement is true, the process stops. If the statement is false, then the alternative route of the connection that failed f is completed in step 48 ahead of all or part of the network connection c. If connection parts c, that is, links for connection c, are not used by connection f, they are marked as free bandwidth (to be used by subsequent connections).

[0027] In step 49 it is checked whether the alternative routing of the network connection f reaches its intended destination, that is, whether the alternative routing for connection f has been completed. If the connection is completed, the process returns to step 42 in which another connection that has failed f with the smaller slack (f, T) is selected. If the connection is not completed, the process goes to step 44 to continue the alternative connection path f with prioritization over additional network connections c.

[0028] Although the above flowchart describes a single failure event in a ring network, the present invention performs the process flow for future failure events as in the case of the previously mentioned mesh networks.

[0029] Network Operations in General

[0030] The above descriptions with respect to Figures 2 and 3 refer to the network operations of the entire network. Priority determination operations could be specifically performed by the network nodes, a network management station, or a network billing system. If the priority determinations are made by the network nodes, the node that detects the link failure in a mesh network makes the priority determinations for its network connections or the priority can also be determined by the originating node of the network. network connection failed on the link that failed. In the latter case, the node that detects the fault must, of course, transmit this information to all nodes affected by the fault.

[0031] Instead of the network nodes, a network management station can determine the network connection priorities. Any information on tracking the downtime per network connection through the SLA period, which allows an SP to prove that an SLA has been met, is more likely to reside at the network management station, rather than at the level of network node where connection prioritization takes place. Therefore, it may be easier for the network management station to determine the network connection priorities.

[0032] Figure 4 illustrates an exemplary mesh network with nodes 50 and a network management station 51 which monitors the operation of the network by direct communication with each of the nodes 50, as shown through the dotted lines. For nodes that are not directly connected to station 51, network management is performed through the network links through an optical service channel. The network management station 51 tracks network failures and measures the actual downtime for each connection. In operation, the network management station provides the nodes of the network with the priorities of each of the network connections and then regularly updates the nodes of the network 50 with new priority values in response to the failures that They have occurred in the intervening period. As stated above, the network management station 51 determines the priority of each network connection based on the actual idle time of the connection and the allowed idle time of the connection SLA and the actual idle time. Even the expected downtime of the connection can also be used. The new priority values prepare the nodes for the next fault. As an alternative, the network management station 51 can again give priority to the nodes after each failure.

[0033] A network billing system 52 can also be used to determine the priorities of the network connections. Since a service provider charges network users, the network operates with a network billing system installed within, or as shown in Figure 3 connected to, network management station 51. The network system Network billing 52 keeps a record of each connection, including its allowed downtime according to its SLA and its actual downtime, to be able to justify user invoices. Therefore, the information for determining the connection priority is readily available for making priority determinations and the communication to the nodes 50 is done through the network management station 51.

[0034] The network nodes, the network management station or the network billing system are adapted to determine connection priorities. One or more integrated circuits, such as an ASIC (Specific Application Integrated Circuit) or an FPGA (Field Programmable Gate Array), can be used at the nodes, at the station or in the system to carry out these determination operations. This hardware implementation allows high speed operations.

[0035] On the other hand, the present invention could be implemented in more conventional integrated circuit arrangements. Firmware, such as the ROM (Read-Only Memory) of a microcontroller, or software can be used with these provisions and offer certain advantages. For example, a processor unit can also perform operations with the software instructions. Figure 5 shows a block diagram of a representative computer system 60 that can be used to execute the software of an embodiment of the invention. The computer system 60 includes a memory 62 that can store and retrieve software programs that incorporate the computer code that implements aspects of the invention, the data for use with the invention, and the like. Examples of computer readable storage media include CD-ROM, floppy disk, tape, flash memory, semiconductor system memory, and hard disk drive. The computer system 60 further includes subsystems such as a central processor 61, fixed storage 64 (for example, hard disk drive), removable storage 66 (for example, CD-ROM), and one or more network interfaces 67 , all connected by a system 68 bus. More or less subsystems can be used. For example, the computer system 60 may include more than one processor 61 (ie, a multi-processor system) or a cache.

[0036] Other embodiments of the present invention

[0037] There are many ways to determine the priority in accordance with the present invention. If the network connections are not operating under SLAs, only the actual downtime of a network connection is used to determine the priority of the connection in a link failure. This allows the downtime caused by the failure to be shared by the network connections in a prescribed and orderly manner.

[0038] As a further example of the priority determination according to the present invention, the previous definition of Slack assumes that there is some data on the reliability of an end-to-end route, that is, the expected connection downtime for year. In the event that such information is not known, one way to account for the lack of information is simply to assume that the expected downtime for the year is the downtime allowed for the year. This represents a more conservative approach that ensures that a connection is on its way to complying with its SLA, regardless of how likely its trajectory will fail.

[0039] Another embodiment of the present invention determines the priority of a network connection based on its allowed idle time from its SLA and the connection link failures themselves. Instead of tracking the history of interruptions for a connection for a prolonged period of time (for example, one year) and determining the priority of the connection based on the recorded downtime, the priority of a connection simply drops exponentially. in time if the connection does not experience failures and rises in case of failure. This allows a variable priority without the requirement of extensive memory to track the downtimes experienced by the connections.

[0040] In the above descriptions, it was assumed that the SLA is defined in terms of downtime per year. A single significant interruption could allow establishing the priorities of the connections and still comply with the terms of the SLA. In contrast, customer expectations cannot be achieved due to the long interruption of services. Consequently, the Slack function of each connection can be recalculated during the interruption period so that if a connection that was not recovered based on its initial priority is close to violating its SLA, its priority will be reconsidered. Alternatively, an SLA can be defined with two time periods: (1) the total interruption allowed for one year, and (2) the maximum contiguous interruptions allowed. In this case, the Slack function represents both time frames in determining the priority of a connection. This guarantees that the downtime of a fault is limited and that the period of interruption of a connection is not excessive.

[0041] Finally, since at least one embodiment of the present invention works to advance connections with maximum Slack, it may be desirable to redirect connections based on knowledge of Slack in the network. This requires changes in the topology broadcast protocols, such as OSPF (Open Shortest Path First), of the network. There are two possible approaches without incorporation through connection data in the disseminated information. For networks that operate with predefined backup routes, such as MPLS (Multiprotocol Label Switching) FRR (Fast Redirect) or SONET mesh protection, there is no need for real-time routing decisions, so there is no need to change OSPF. The same is true for ring networks. For other networks, it is sufficient to add fault statistics for each link in the network, instead of adding data per connection. Since most failures are due to fiber cuts, this minimum information is sufficient to calculate the Slack for a particular route.

 [0042] Therefore, while the above description provides a full and complete description of the preferred embodiments of the present invention, various modifications, alternative constructions, and equivalents will be apparent to those skilled in the art. Therefore, the scope of the present invention is limited only by the objectives and limits of the appended claims.

[0043] This description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or limit the invention to the precise manner described, and many modifications and variations are possible in light of the prior teaching. The embodiments have been chosen and described in order to better explain the principles of the invention and their practical applications. This description will allow other persons skilled in the art to better utilize and carry out the invention in various embodiments and with various modifications that are suitable for a particular use. The scope of the invention is defined by the following claims.

Claims (8)

1. A method for operating a communications network that has a plurality of links and that carries a plurality of network connections comprising: determining a priority of each of a plurality of network connections intended to communicate over a communications link based on a corresponding predetermined stop time; detect (30) a failure in the communications link at a point at time T; calculate a real stop time for each of the plurality of network connections of an amount of interruption that has occurred during a predetermined period of time until time T; calculate an allowed stop time for each of the plurality of network connections from an allowable interruption amount over the predetermined period of time; calculate an expected stop time for each of the plurality of network connections of an expected amount of interruption from time T to an end of the predetermined period of time; protect the plurality of network connections from failure in the communications link according to the given priority of each of the plurality of network connections, in which a network connection with a higher priority supplants a connection with a lower priority; Y update (34) the priority of each of the plurality of network connections from a time from the calculation of the actual stop time and the stop time allowed to increase the priority for each of the plurality of network connections as the actual stop time approaches the allowed stop time for each of the plurality of network connections.

2.

The method of claim 1, wherein updating also comprises updating the priority for each of the plurality so that a number of network connections with the calculated actual stop time that exceeds the calculated allowed stop time is minimized.

3.

The method of claim 2, further comprising detecting a second fault within the predetermined period at a second point in time and updating the priority for each of the plurality of network connections from a time from the second point on the time and from the allowable stop time calculated so that the number of network connections with the calculated actual stop time that exceeds the calculated expected stop time is minimized during the second fault.

Four.

The method of claim 1, further comprising calculating a hollow period that represents a remaining allowed stop time for each of the network connections within the predetermined period of time from the calculated allowed stop time, the actual stop time calculated, and the expected stop time calculated for a period of time remaining within said predetermined period of time.

5.

The method of claim 4, wherein updating comprises updating the priority of the network connections from the hollow period.

6.

The method of claim 1, wherein updating comprises updating the priority of the network connections from a cumulative actual stop time for a plurality of predetermined periods.

7.

An apparatus comprising:

a network interface configured to communicate over a communications network having a plurality of nodes connected by a plurality of links, each link having a plurality of network connections; Y at least one integrated circuit configured to perform a method according to any of the preceding claims. 8. A computer-readable medium that includes executable instructions that, when executed in a processing system, causes the processing system to perform a procedure according to any one of claims 1 to 6. Network billing system Network management station